The fuel economy of a vehicle can be approximated using different methods based on the actual performance of a vehicle. That is, by measuring the vehicle's actual performance, the fuel economy of the vehicle may be quantified and displayed on an in-vehicle display. More practically, a fuel economy of the vehicle or “mpg” may be quantified from actual vehicle performance measurements and factors associated with a driver's driving behavior and displayed to the driver. By viewing the fuel economy display, a driver may be able to understand how the driver's driving behavior influences the vehicle's fuel economy. The fuel economy is typically measured and displayed in values such as miles per gallon (mpg) or kilometers per liter (km/L), and fuel economy may be displayed as both instantaneous and average values. Patent document 1, i.e., Japanese Publication 2011-117838, discloses measuring a vehicle's fuel economy and displaying the fuel economy on an in-vehicle display.
Patent document 1 discloses a display controller that calculates and displays a specific-driver-related fuel economy based on specific vehicle performance for each driving instance (i.e., trip) driven by the driver. The specific-driver-related fuel economy calculation may be compared with a baseline value that represents an average fuel economy of many drivers or the fuel economy based on an average driver. In other words, displaying the difference between the specific-driver-related fuel economy calculation and the baseline value can serve as a base to illustrate trends showing whether a driver's driving behavior is leading to a better-than-average fuel economy or alert a driver that there may be room for improvement.
By viewing such a difference, the driver is better able to grasp whether there has been any improvement to the driver-specific fuel economy. That is, the driver may strive to continue fuel-efficient driving behavior to stay ahead of the baseline fuel economy level or may be motivated to further improve such driving behavior. As such, the display controller may not only be used to inform the driver, but also provide some fun to a driver by motivating a driver to exhibit driving behavior to reach a certain fuel economy goal.
The previously-described baseline fuel economy value may be calculated as the average fuel economy based on many different driving events or trips.
In such case, an average of the driver-specific fuel economy to derive a driver-specific baseline value may only be calculable after a certain number of drive events/trips. That is, the driver may have to drive the vehicle many times before the display device displays a driver's baseline fuel economy and +/− trend value illustrating the difference from the baseline value. For example, a driver of a new vehicle may wonder how many times the vehicle must be driven in order to calculate and display the baseline fuel economy and +/− trend, and the driver may suspect that such functionality and display may be malfunctioning and/or defective.
However, the fuel economy +/− trend may be more quickly displayed after using the vehicle, for example, by a method that averages the driver-specific fuel economy from all previous trips (i.e., driving events) to calculate the baseline fuel economy.
However, such a method of calculating the baseline value may be prone to large value fluctuations due to the small sample size. That is, when a vehicle is first used, the baseline fuel economy used to show +/− trends may largely fluctuate based on the small sample size, i.e., small number of previous trips used to calculate the baseline. In other words, the weight of each sampled value used to calculate the baseline value may be very large and this in turn may result in the display of +/− trends that largely differ from one driving instance (i.e., trip) to another. As such, the driver may be misled by large fluctuations in the fuel economy trends.